Photoelectric conversion device, photoelectric conversion system, and moving body

ABSTRACT

A photoelectric conversion device includes a photoelectric converter, a first node configured to be supplied with charges from the photoelectric converter, an amplification transistor configured to output a signal corresponding to a voltage of the first node, a first transistor configured to open/close a path between the first node and a second node not included in a path from the photoelectric converter to the first node, and a second transistor configured to open/close a path between the second node and a third node. A second capacitance which is added to the second node when the second transistor is set in a conductive state is larger than a first capacitance which is added to the first node when the first transistor is set in a conductive state.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a photoelectric conversion device, aphotoelectric conversion system, and a moving body.

Description of the Related Art

Japanese Patent Laid-Open No. 2020-039114 discloses an arrangementincluding the first capacitance addition transistor having one endconnected to a floating diffusion unit (to be referred to as an FD unithereinafter) and the other end connected to a reset transistor in orderto expand the dynamic range in an image capturing device. JapanesePatent Laid-Open No. 2020-039114 also discloses an arrangement includingthe second capacitance addition transistor between the reset transistorand the first capacitance addition transistor. Furthermore, JapanesePatent Laid-Open No. 2020-039114 discloses an arrangement of applying anintermediate voltage between high level and low level to the resettransistor, the first capacitance addition transistor, or the secondcapacitance addition transistor in order to suppress the voltageamplitude of the FD unit corresponding to a high luminance signal.

SUMMARY OF THE INVENTION

One of aspects of the present invention provides a photoelectricconversion device comprising: a photoelectric converter; a first nodeconfigured to be supplied with charges from the photoelectric converter;an amplification transistor configured to output a signal correspondingto a voltage of the first node; a first transistor configured toopen/close a path between the first node and a second node not includedin a path from the photoelectric converter to the first node; and asecond transistor configured to open/close a path between the secondnode and a third node, wherein a second capacitance which is added tothe second node when the second transistor is set in a conductive stateis larger than a first capacitance which is added to the first node whenthe first transistor is set in a conductive state.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments with reference to theattached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing the arrangement of an image capturingdevice according to the first to third embodiments;

FIG. 2 is an equivalent circuit diagram showing the arrangement of apixel according to a comparative example;

FIG. 3 is an equivalent circuit diagram showing the arrangement ofpixels according to another comparative example and the firstembodiment;

FIG. 4 shows plan views of the arrangements (layouts) of the pixelsaccording to the comparative example, the other comparative example, andthe first embodiment;

FIG. 5 is a table for explaining the first embodiment;

FIG. 6 is a table for explaining the first embodiment;

FIG. 7 is a graph for explaining the first embodiment;

FIG. 8 is a table for explaining an image capturing device according tothe second embodiment;

FIG. 9 is a circuit diagram showing the arrangement of a pixel accordingto the second embodiment;

FIG. 10 is a plan view showing the arrangement (layout) of the pixelaccording to the second embodiment;

FIG. 11 is an equivalent circuit diagram showing the arrangement of apixel according to the third embodiment;

FIG. 12 is a plan view showing the arrangement (layout) of the pixelaccording to the third embodiment;

FIG. 13 is a table for explaining an image capturing device according tothe third embodiment;

FIG. 14 is a block diagram showing the arrangement of a photoelectricconversion system according to an embodiment;

FIGS. 15A and 15B show views of the arrangement of a vehicle system anda photoelectric conversion system that is incorporated in the vehiclesystem and performs image capturing according to an embodiment; and

FIG. 16 is a flowchart illustrating the operation of the photoelectricconversion system shown in FIGS. 15A and 15B.

DESCRIPTION OF THE EMBODIMENTS

Hereinafter, embodiments will be described in detail with reference tothe attached drawings. Note, the following embodiments are not intendedto limit the scope of the claimed invention. Multiple features aredescribed in the embodiments, but limitation is not made to an inventionthat requires all such features, and multiple such features may becombined as appropriate. Furthermore, in the attached drawings, the samereference numerals are given to the same or similar configurations, andredundant description thereof is omitted.

FIG. 1 shows the schematic arrangement of an image capturing device 1according to the first embodiment. The image capturing device 1 caninclude, for example, a pixel array 100, a vertical scanning circuit101, an amplifier circuit 102, a horizontal scanning circuit 103, anoutput circuit 104, and a control circuit 105. The pixel array 100 caninclude a plurality of pixels 20 arranged to form a plurality of rowsand a plurality of columns. The vertical scanning circuit 101 can beconfigured to select the plurality of pixel 20 on the row basis. Thevertical scanning circuit 101 can be configured to drive a plurality ofcontrol lines for controlling the pixels 20 of the respective rows. Thevertical scanning circuit 101 can include, for example, a logic circuitsuch as a shift resistor and/or address decoder.

Each column of the pixel array 100 is provided with a vertical outputline 10, and pixel signals from the pixels 20 can be output to thevertical output line 10 for each column. The amplifier circuit 102amplifies the pixel signals output to each vertical output line 10, andcan perform correlated double sampling processing based on signals atthe time of reset and photoelectrically converted signals. The amplifiercircuit 102 can include a plurality of column amplifiers correspondingto the plurality of vertical output lines 10 of the pixel array 100,respectively. The horizontal scanning circuit 103 selects outputs fromthe plurality of column amplifiers of the amplifier circuit 102 in apredetermined order and supplies them to the output circuit 104. Theoutput circuit 104 is formed by, for example, a differential amplifier,a buffer amplifier, and the like, and can output, to an external orinternal device (for example, a processor) of the image capturing device1, the pixel signals supplied from the amplifier circuit 102. The imagecapturing device 1 may include an A/D converter. The pixel array 100 maybe formed by the plurality of pixels 20 which are one-dimensionallyarranged. Alternatively, the pixel array 100 may be replaced by onepixel 20.

FIG. 2 is an equivalent circuit diagram showing the arrangement of apixel 20A according to a comparative example. FIG. 2 shows three pixels20A of 1 row×3 columns among the plurality of pixels 20A which aretwo-dimensionally arranged in a pixel array 100 to form a plurality ofrows and a plurality of columns. However, the pixel array 100 can beformed by more pixels 20A. Each pixel 20A can include a photodiode (tobe referred to as a PD hereinafter) 201 as a photoelectric converter, atransfer transistor 202, and a floating diffusion 203 (to be referred toas an FD 203 or a first node n1 hereinafter) functioning as acharge-to-voltage converter. Each pixel 20A can also include a resettransistor 204, an amplification transistor 205, and a selectiontransistor 206. The first electrode (for example, an anode) of the PD201 can be connected to a first voltage line (for example, a groundline) 208. The second electrode (for example, a cathode) of the PD 201can be connected to the FD 203 via the transfer transistor 202. In otherwords, the transfer transistor 202 transfers charges from the PD 201 tothe FD 203. When a transfer signal φ202(n) supplied from a verticalscanning circuit 101 to the gate of the transfer transistor 202 via atransfer signal line is set to the active level, the transfer transistor202 can transfer charges from the PD 201 to the FD 203. The transfertransistor 202 is an optional component and may be eliminated.

When a reset signal φ204(n) supplied from the vertical scanning circuit101 to the gate of the reset transistor 204 via a reset signal line isset to the active level, the reset transistor 204 can reset the voltagesof the second electrode (for example, the cathode) of the PD 201 and theFD 203. The amplification transistor 205 can output a signalcorresponding to the voltage of the FD 203 to a vertical output lineVout. The amplification transistor 205 can form a source followercircuit together with a current source (not shown) connected to thevertical output line Vout. The vertical output line Vout is the verticaloutput line 10 shown in FIG. 1 . In FIG. 2 , to identify a column, asubscript is added to Vout like Vout(m−1), Vout(m), and Vout(m+1). Whena selection signal φ206(n) supplied from the vertical scanning circuit101 to the gate of the selection transistor 206 via a selection signalline is set to the active level, the selection transistor 206electrically connects the amplification transistor 205 to the verticaloutput line Vout. The selection transistor 206 is an optional componentand may be eliminated. In this case, the selected state and theunselected state of the pixel 20 can be distinguished from each other inaccordance with a voltage set in the FD 203 at the time of reset.

The pixel 20A further includes a first transistor 210 in a path betweenthe first node n1 (FD 203) and a second node n2 or the reset transistor204. The second node n2 is a node that is not included in the path fromthe PD 201 to the first node n1. The first transistor 210 includes thefirst electrode (for example, a drain) connected to the first node n1 orthe FD 203, and the second electrode (for example, a source) connectedto the second node n2 or the first electrode (for example, a drain) ofthe reset transistor 204. The first transistor 210 functions as acapacitance addition transistor for adding a capacitance to the firstnode or the FD 203 (capacitance thereof). The capacitance that is addedto the first node or the FD 203 (capacitance thereof) when the firsttransistor 210 is set in the conductive state (turned on) will bereferred to as the capacitance (first capacitance) of the firsttransistor 210. When a sensitivity control signal φ210(n) supplied fromthe vertical scanning circuit 101 to the gate of the first transistor210 via a sensitivity control line is set to the active level, the firsttransistor 210 is set in the conductive state. If the capacitance of thefirst transistor 210 is added to the first node n1 or the FD 203(capacitance thereof), the capacitance of the first node n1 or the FD203 and the capacitance of the first transistor 210 function as acharge-to-voltage converter, and thus the sensitivity for convertingcharges into a voltage deteriorates.

The first transistor 210 may be arranged in parallel with the resettransistor 204. In this case, however, even when the first transistor210 is in the non-conductive state, the parasitic capacitance of the FD203 increases, and thus the sensitivity for converting charges into avoltage deteriorates. Therefore, the first transistor 210 and the resettransistor 204 are preferably connected to the FD 203 in series.

When light enters the PD 201, photoelectric conversion occurs in the PD201, and the thus generated charges can be accumulated in the chargeaccumulation region of the PD 201. When the transfer signal φ202(n) isset to the active level, the transfer transistor 202 is set in theconductive state to transfer the charges of the PD 201 to the FD 203.The amplification transistor 205 forms a source follower circuit, andcan output a signal corresponding to the voltage of the FD 203 to thevertical output line 10 via the selection transistor 206.

If the first transistor 210 is in the non-conductive state (OFF state),the charges transferred from the PD 201 by the transfer transistor 202are held by only the capacitance of the FD 203. On the other hand, ifthe first transistor 210 is in the conductive state (ON state), thecharges transferred from the PD 201 by the transfer transistor 202 areheld by the capacitance of the FD 203 and the capacitance of the firsttransistor 210. That is, under the control of the first transistor 210,the capacitance for holding the charges transferred from the PD 201 bythe transfer transistor 202 can be changed. By simultaneously settingthe reset transistor 204 and the first transistor 210 in the conductivestate, the voltage of the FD 203 can be reset to a voltage correspondingto the voltage of a first voltage line 209.

The vertical scanning circuit 101 supplies a common control signal toeach pixel 20A of the same row. That is, the control signals φ202(n),φ204(n), φ206(n), and φ210(n) are supplied to the transfer transistors202, the reset transistors 204, the selection transistors 206, and thefirst transistors 210 of the nth row, respectively. These transistorsare turned on when the control signals are at high level, and are turnedoff when the control signals are at low level. While the signal φ210(n)is at high level, the first transistor 210 can connect the firstcapacitance to the FD 203.

The first transistor 210 will now be described in more detail. The firsttransistor 210 includes one electrode (source) connected to the FD 203.When the first transistor 210 is set in the conductive state, a channelis formed in the first transistor 210, and a capacitance (MOScapacitance) by this channel is added to the capacitance of the FD 203.Furthermore, the parasitic capacitance of the other electrode (drain) ofthe first transistor 210, for example, the capacitance between the gateelectrode and the other electrode (drain), the p-n junction capacitanceof a semiconductor region forming the other electrode, and thecapacitance with the peripheral wiring are added to the capacitance ofthe FD 203. When the capacitance is added to the FD 203 to increase thecapacitance of the charge-to-voltage converter, charges that can be heldby the charge-to-voltage converter increase, thereby expanding thedynamic range. If the first transistor 210 is set in the non-conductivestate, the capacitance of the first transistor 210 is not added to theFD 203. In this case, the sensitivity (for example, a voltage changeamount (charge-to-voltage conversion efficiency) with respect to onecharge) of the pixel 20A or the FD 203 can be improved. Thus, under thecontrol of the first transistor 210, the sensitivity of the pixel 20Acan be changed.

FIG. 3 is an equivalent circuit diagram showing the arrangement of apixel 20B according to another comparative example and a pixel 20Caccording to the first embodiment. The pixels 20B and 20C have the samearrangement in the equivalent circuit. Each of the pixels 20B and 20Chas the arrangement obtained by adding a second transistor 211 to thepixel 20A. When a sensitivity control signal φ211(n) supplied from avertical scanning circuit 101 to the gate of the second transistor 211via a sensitivity control line is set to the active level, the secondtransistor 211 is set in the conductive state. As described above, if afirst transistor 210 is set in the conductive state, the capacitance(first capacitance) of the first transistor 210 is added to thecapacitance of an FD 203 or a first node n1. If the second transistor211 is set in the conductive state while the first transistor 210 is inthe conductive state, the capacitance (second capacitance) of the secondtransistor 211 is added to the capacitance of the FD 203 in addition tothe capacitance of the first transistor 210. At this time, thecapacitance of the second transistor 211 is a capacitance to be added toa second node n2 when the second transistor 211 is set in the conductivestate.

Each of the pixels 20B and 20C includes a PD 201 as a photoelectricconverter, the first node n1 (FD 203) that is supplied with charges fromthe PD 201, and an amplification transistor 205 that outputs a signalcorresponding to the voltage of the first node n1. Each of the pixels20B and 20C can also include the first transistor 210 that opens/closesa path between the first node n1 and the second node n2, and the secondtransistor 211 that opens/closes a path between the second node n2 and athird node n3. Furthermore, each of the pixels 20B and 20C can include atransfer transistor 202, a reset transistor 204, and a selectiontransistor 206.

When a transfer signal φ202(n) supplied from the vertical scanningcircuit 101 to the gate of the transfer transistor 202 via a transfersignal line is set to the active level, the transfer transistor 202 cantransfer charges from the PD 201 to the first node n1 (FD 203). Thetransfer transistor 202 is an optional component and may be eliminated.When a reset signal φ204(n) supplied from the vertical scanning circuit101 to the gate of the reset transistor 204 via a reset signal line isset to the active level, the reset transistor 204 can reset the voltagesof the second electrode of the PD 201 and the first node n1 (FD 203).When a selection signal φ206(n) supplied from the vertical scanningcircuit 101 to the gate of the selection transistor 206 via a selectionsignal line is set to the active level, the selection transistor 206 canelectrically connect the amplification transistor 205 to a verticaloutput line Vout. The selection transistor 206 is an optional componentand may be eliminated. In this case, the selected state and theunselected state of the pixel 20 can be distinguished from each other inaccordance with a voltage set in the FD 203 at the time of reset.

When the first transistor 210 and the second transistor 211 areprovided, the capacitance of the charge-to-voltage converter includingthe FD 203 can be changed in three stages. That is, the capacitance ofthe charge-to-voltage converter can be selected from capacitances ofthree stages. The capacitance of the first stage is the capacitance(that is, the capacitance of only the FD 203) of the charge-to-voltageconverter when the first transistor 210 is in the non-conductive state.The capacitance of the second stage is the capacitance (that is, the sumof the capacitance of the FD 203 and the first capacitance of the firsttransistor 210) of the charge-to-voltage converter when the firsttransistor 210 is in the conductive state and the second transistor 211is in the non-conductive state. The capacitance of the third stage isthe capacitance (that is, the sum of the capacitance of the FD 203, thefirst capacitance of the first transistor 210 and the second capacitanceof the second transistor 211) of the charge-to-voltage converter whenthe first transistor 210 and the second transistor 211 are in theconductive state.

The arrangements of the pixel 20A (comparative example), the pixel 20B(other comparative example), and the pixel 20C will be described withreference to FIG. 4 . In FIG. 4 , (a) shows the arrangement of the pixel20A, (b) shows the arrangement of the pixel 20B, and (c) shows thearrangement of the pixel 20C. The pixel 20A includes only the firsttransistor 210 as a transistor for controlling the capacitance of thecharge-to-voltage converter. On the other hand, each of the pixels 20Band 20C includes the first transistor 210 and the second transistor 211as transistors for controlling the capacitance of the charge-to-voltageconverter.

The difference between the pixels 20B and 20C is the magnituderelationship between the capacitances of the first transistor 210 andthe second transistor 211. While the capacitance of the first transistor210 is larger than that of the second transistor 211 in the pixel 20B,the capacitance of the second transistor 211 is larger than that of thefirst transistor 210 in the pixel 20C. In this example, the capacitancesof the first transistor 210 and the second transistor 211 can beproportional to the gate lengths, respectively. While the gate length ofthe first transistor 210 is longer than that of the second transistor211 in the pixel 20B, the gate length of the second transistor 211 islonger than that of the first transistor 210 in the pixel 20C. In thepixels 20B and 20C, the gate width of the first transistor 210 is equalto that of the second transistor 211. However, the gate widths of thefirst transistor 210 and the second transistor 211 may be different fromeach other.

FIG. 5 exemplifies the capacitances of the FD 203, the first transistor210, and the second transistor 211 in each of the pixels 20A, 20B, and20C. In the example shown in FIG. 5 , in the pixel 20A, the capacitanceof the FD 203 is 0.25 [F], the capacitance of the first transistor 210is 0.75, and the sum of the capacitances is 1 [F]. In the pixel 20B, thecapacitance of the FD 203 is 0.25 [F], the capacitance of the firsttransistor 210 is 0.50 [F], the capacitance of the second transistor 211is 0.25 [F], and the sum of the capacitances is 1 [F]. Furthermore, inthe pixel 20C, the capacitance of the FD 203 is 0.25 [F], thecapacitance of the first transistor 210 is 0.25 [F], the capacitance ofthe second transistor 211 is 0.50 [F], and the sum of the capacitancesis 1 [F]. That is, FIG. 5 shows an example of the pixel 20B in which thecapacitance of the first transistor 210 is larger than that of thesecond transistor 211, and an example of the pixel 20C in which thecapacitance of the second transistor 211 is larger than that of thefirst transistor 210.

FIG. 6 exemplifies a gain, the number of signal charges, the capacitanceof the charge-to-voltage converter, the number of noise charges of thecharge-to-voltage converter, a signal output (S), a noise output (N),and an N/S ratio in each of the pixels 20A, 20B, and 20C. The gain of acolumn a is the gain (in this example, the gain is represented by[times]) of the image capturing device 1. The number of signal chargesof a column b is the number of signal charges (in this example, chargesare electrons) necessary to output a saturation signal corresponding tothe gain. The saturation signal is the upper limit of an output in acaptured image, which corresponds to each gain. If the number of signalcharges necessary when the gain is 1 [times] is 1,000 [electrons], thenumber of signal charges necessary when the gain is 2 [times] is 500[electrons]. The capacitance of a column c is a selectable optimumcapacitance (in this example, farad [F]) of the charge-to-voltageconverter to convert the number of signal charges indicated in thecolumn b into a voltage. This indicates that if the number of signalcharges is 1,000 [electrons], the optimum capacitance of thecharge-to-voltage converter is 1 [F].

With respect to the pixel 20A, when the gain is 2 [times], thecapacitance of the charge-to-voltage converter is 0.5 [F] which is ½ ofthe capacitance when the gain is 1 [times]. However, as shown in FIG. 5, the capacitance of the first transistor 210 is 0.75 [F] and thus thefirst transistor 210 cannot be turned off. When the gain is 4 [times],the capacitance of the charge-to-voltage converter is 0.25 [F] which is¼ of the capacitance when the gain is 1 [times], and the firsttransistor 210 can be turned off.

With respect to the pixel 20B, when the gain is 2 [times], thecapacitance of the charge-to-voltage converter is 0.5 [F] which is ½ ofthe capacitance when the gain is 1 [times]. As shown in FIG. 5 , thecapacitance of the second transistor 211 is 0.25 [F] and thus the secondtransistor 211 can be turned off.

When the gain is 4 [times], the capacitance of the charge-to-voltageconverter is 0.25 [F] which is ¼ of the capacitance when the gain is 1[times], and the first transistor 210 can be turned off.

With respect to the pixel 20C, when the gain is 2 [times], thecapacitance of the charge-to-voltage converter is 0.5 [F] which is ½ ofthe capacitance when the gain is 1 [times]. As shown in FIG. 5 , thecapacitance of the second transistor 211 is 0.50 [F] and thus the secondtransistor 211 can be turned off.

When the gain is 4 [times], the capacitance of the charge-to-voltageconverter is 0.25 [F] which is ¼ of the capacitance when the gain is 1[times], and the first transistor 210 can be turned off.

The number of noise charges of a column d is the number of noise chargesgenerated in the charge-to-voltage converter in accordance with thecapacitance of the charge-to-voltage converter indicated in the columnc. If noise generated when the capacitance of the charge-to-voltageconverter is 1 [F] is 100 [electrons], it can be estimated that noisegenerated when the capacitance of the charge-to-voltage converter is 0.5[F] is 50 [electrons]. When paying attention to the case in which thegain is 2 [times], the number of noise charges of the pixel 20A is 100[electrons]. On the other hand, since it is possible to turn off thefirst transistor 210 in the pixel 20B, the capacitance of thecharge-to-voltage converter decreases to 0.75 [F], and the number ofnoise charges is reduced to 75 [electrons]. Furthermore, in the pixel20C, the capacitance of the second transistor 211 is large, as comparedwith the pixel 20B. Therefore, in the pixel 20C, the capacitance of thecharge-to-voltage converter decreases to 0.50 [F] by turning off thesecond transistor 211, and the number of noise charges is reduced to 50[electrons].

The signal output of a column e is a saturation signal output (S signal)based on the gain indicated in the column a and the number of signalcharges indicated in the column b. The noise output of a column f is anoise output (N signal) based on the gain indicated in the column a andthe number of noise charges indicated in the column d. For example,between a case in which the gain is 4 [times] and a case in which thegain is 8 [times], the capacitance of the charge-to-voltage converterremains the same and thus the number of noise charges remains unchangedbut the N signal increases.

The N/S ratio of a column g is an N/S ratio as the ratio between the Ssignal and the N signal indicated in the columns e and f, respectively.A low N/S ratio indicates that the ratio of noise in the captured imageis low and more satisfactory image quality is obtained. When payingattention to the case in which the gain is 2 [times], the N/S ratiodecreases in the pixel 20B with respect to the pixel 20A, and furtherdecreases in the pixel 20C with respect to the pixel 20B.

FIG. 7 shows the N/S ratios in the pixels 20A, 20B, and 20C shown inFIG. 6 . The abscissa represents the gain indicated in the column a ofFIG. 6 and the ordinate represents the N/S ratio indicated in the columng of FIG. 6 . As described above, when paying attention to the N/S ratiowhen the gain is 2 [times], it is indicated that the N/S ratio in thepixel 20B is lower than that in the pixel 20A and satisfactory imagequality is obtained, and the N/S ratio in the pixel 20C is lower thanthat in the pixel 20B and more satisfactory image quality is obtained.Note that when the gain is 4 [times] or more, the capacitances of thecharge-to-voltage converters are the same in the pixels 20A, 20B, and20C and thus the N/S ratios remain unchanged.

As described above, in the first embodiment, in the arrangement in whichthe first transistor 210, the second transistor 211, and the resettransistor 204 are connected in series to the FD 203, the capacitance ofthe second transistor 211 is larger than that of the first transistor210. This can provide satisfactory image quality with a low N/S ratio.

Note that it is also possible to make settings so that the capacitanceof the FD 203, that of the first transistor 210, and that of the secondtransistor 211 are the same. Since, however, the gain of the imagecapturing device 1 changes by the power of 2, the ratio of eachcapacitance is desirably set, as in the above-described example.

Each of the capacitances (capacitance values) of the first transistor210 and the second transistor 211 can be decided appropriately byadjusting the design of the transistor, a relative arrangement withrespect to another wiring, and the like. Among others, the capacitance(MOS capacitance) obtained by forming the channel of the transistor hasthe highest capacity density, and thus adjustment of the area of thetransistor (gate) is most efficient. On the other hand, if the area ofthe transistor (gate) is increased, for example, the area of the PD canbecome small. If the area of the PD becomes small, this may decrease thesensitivity, or decrease the saturated charge amount, which can beaccumulated in the PD, to reduce the dynamic range.

It can be understood that the pixel 20C shown in (c) of FIG. 4 has astructure obtained by dividing the first transistor 210 of the pixel 20Ashown in (a) of FIG. 4 into the first transistor and the secondtransistor 211. In the pixel 20C, the area ratio between the gate of thefirst transistor 210 and that of the second transistor 211 is almostequal to the ratio between the gate length of the first transistor 210and that of the second transistor 211. That is, the fact that thecapacitance of the second transistor 211 is larger than that of thefirst transistor 210 indicates that the gate length of the secondtransistor 211 is longer than that of the first transistor 210. Ingeneral, the transistor exhibits a roll-off characteristic with respectto the gate length. According to this, in the pixel 20C, the thresholdof the first transistor 210 with the shorter gate length is smaller thanthat of the second transistor 211 with the longer gate length.

The thresholds and driving operations of the first transistor 210 andthe second transistor 211 will now be described with reference to FIG. 8. FIG. 8 shows the driving operations of the first transistor 210, thesecond transistor 211, and the reset transistor 204 in a readoutoperation of a pixel signal. In operation A, the sensitivity controlsignals φ210 and φ211 are set to the active level (the first transistor210 and the second transistor 211 are ON). Furthermore, in operation A,the reset signal φ204 changes like a pulse. This resets the capacitancesof the FD 203, the first transistor 210, and the second transistor 211.In operation B, the signals φ210 and φ204 are set to the active level(the first transistor 210 and the reset transistor 204 are ON).Furthermore, in operation B, the signal φ211 changes like a pulse. Thisresets the capacitances of the FD 203 and the first transistor 210. Inoperation C, the signals φ211 and φ204 are set to the active level (thesecond transistor 211 and the reset transistor 204 are ON). Furthermore,in operation C, the signal φ210 changes like a pulse. This resets the FD203.

In operation A, the second transistor 211 is continuously in the ONstate. However, if the threshold of the second transistor 211 is large,the voltage dependency of the capacitance of the second transistor 211,which depends on the operation point of the FD 203, may become large.That is, there may be a difference between the capacitance of the secondtransistor 211 at the time of low luminance when the voltage of thecharge-to-voltage converter including the FD 203 is high and that at thetime of high luminance when the voltage of the charge-to-voltageconverter is low. In this case, since the charge-to-voltage conversionefficiency changes depending on the luminance, the realitycharacteristic may deteriorate.

On the other hand, there is provided a method of decreasing thethreshold of the second transistor 211 by adjusting the concentration ofan impurity implanted to the channel of the second transistor 211. Ifthe threshold of the second transistor 211 is decreased, the voltagedependency of the capacitance of the second transistor 211 is improvedbut another problem may arise. In operation B, the capacitances of theFD 203 and the first transistor 210 are reset by turning on and off thesecond transistor 211 by the signal φ211 like a pulse. Upon completionof reset, the second transistor 211 is turned off. At this time, if thethreshold of the second transistor 211 is small, the voltage amplitudeof the FD 203 may be limited. That is, if many charges photoelectricallyconverted in the PD 201 in accordance with a high-luminance object aretransferred to the FD 203, the voltage of the FD 203 is to decrease byan amount corresponding to the charges. However, since the secondtransistor 211 operates as an amplitude limiting circuit by the smallthreshold, the second transistor 211 is released from the OFF state, andcan operate so that the FD 203 is maintained at a voltage decided by anoff-leak of the second transistor 211. Therefore, in operation B, whenthe voltage amplitude of the FD 203 is limited, the dynamic range maydecrease.

The second embodiment solves the above problem. FIG. 9 is an equivalentcircuit diagram showing the arrangement of a pixel 20D of an imagecapturing device 1 according to the second embodiment. FIG. 10 shows thearrangement of the pixel 20D. Note that matters not mentioned in thesecond embodiment can comply with the first embodiment.

The pixel 20D according to the second embodiment has an arrangementobtained by adding a third transistor 212 to the pixel 20C of the firstembodiment.

The pixel 20D includes a PD 201 as a photoelectric converter, a firstnode n1 (FD 203) that is supplied with charges from the PD 201, and anamplification transistor 205 that outputs a signal corresponding to thevoltage of the first node n1. The pixel 20D can also include a firsttransistor 210 that opens/closes a path between the first node n1 and asecond node n2, and a second transistor 211 that opens/closes a pathbetween the second node n2 and a third node n3. The pixel 20D caninclude the third transistor 212 that opens/closes a path between thethird node n3 and a fourth node n4. Furthermore, the pixel 20D caninclude a transfer transistor 202, a reset transistor 204, and aselection transistor 206. A fixed potential that always sets the thirdtransistor 212 in the conductive state is applied to the gate of thethird transistor 212. The gate of the third transistor 212 can beconnected to, for example, a first voltage line 209.

It can be understood that the pixel 20D according to the secondembodiment has an arrangement obtained by dividing the second transistor211 of the pixel 20C of the first embodiment into the second transistor211 and the third transistor 212. Since a voltage that always sets thethird transistor 212 in the conductive state is applied to the gate ofthe third transistor 212, it is unnecessary to consider the OFFcharacteristic of the third transistor 212. That is, it is possible tosufficiently decrease the threshold of the third transistor 212, and todecrease the voltage dependency of the capacitance of the thirdtransistor 212, which depends on the operation point of the FD 203. Onthe other hand, it is possible to sufficiently increase the threshold ofthe second transistor 211, and to relax the voltage amplitude limitationof the FD 203. According to the second embodiment, it is possible toimprove the linearity characteristics in operation A and expand thedynamic range in operation B.

The second embodiment shows the example in which the third transistor212 is added. However, more transistors may be added between the firstnode n1 and the reset transistor 204. In this case as well, the gate ofa transistor having one end connected to the reset transistor 204 can beapplied with a voltage that always sets the transistor in the conductivestate.

An image capturing device 1 according to the third embodiment will bedescribed below. FIG. 11 is an equivalent circuit diagram showing thearrangement of a pixel 20E of the image capturing device 1 according tothe third embodiment. FIG. 12 shows the arrangement of the pixel 20E.Note that matters not mentioned in the third embodiment can comply withthe first embodiment. The pixel 20E according to the third embodimenthas an arrangement obtained by adding a third transistor 212 to thepixel 20C of the first embodiment.

When a sensitivity control signal φ212(n) supplied from a verticalscanning circuit 101 to the gate of the third transistor 212 via asensitivity control line is set to the active level, the thirdtransistor 212 is set in the conductive state. As described above, if afirst transistor 210 is set in the conductive state, the firstcapacitance of the first transistor 210 is added to the capacitance ofan FD 203. Furthermore, if a second transistor 211 is set in theconductive state while the first transistor 210 is in the conductivestate, the second capacitance of the second transistor 211 is added tothe capacitance of the FD 203 in addition to the first capacitance ofthe first transistor 210. If the third transistor 212 is set in theconductive state while the first transistor 210 and the secondtransistor 211 are in the conductive state, the third capacitance of thethird transistor 212 is added to the capacitance of the FD 203 inaddition to the first capacitance of the first transistor 210 and thesecond capacitance of the second transistor 211. The third capacitanceof the third transistor 212 is a capacitance to be added to thecapacitance of the FD 203 when the third transistor 212 is set in theconductive state.

The pixel 20E includes a PD 201 as a photoelectric converter, a firstnode n1 (FD 203) that is supplied with charges from the PD 201, and anamplification transistor 205 that outputs a signal corresponding to thevoltage of the first node n1. The pixel 20E can also include the firsttransistor 210 that opens/closes a path between the first node n1 and asecond node n2, and the second transistor 211 that opens/closes a pathbetween the second node n2 and a third node n3. The pixel 20E caninclude the third transistor 212 that opens/closes a path between thethird node n3 and a fourth node n4. Furthermore, the pixel 20E caninclude a transfer transistor 202, a reset transistor 204, and aselection transistor 206.

When the first transistor 210, the second transistor 211, and the thirdtransistor 212 are provided, the capacitance of the charge-to-voltageconverter including the FD 203 can be changed in four stages. That is,the capacitance of the charge-to-voltage converter can be selected fromcapacitances of four stages. The capacitance of the first stage is thecapacitance of the charge-to-voltage converter when the first transistor210 is in the non-conductive state. The capacitance of the second stageis the capacitance of the charge-to-voltage converter when the firsttransistor 210 is in the conductive state and the second transistor 211is in the non-conductive state. The capacitance of the third stage isthe capacitance of the charge-to-voltage converter when the firsttransistor 210 and the second transistor 211 are in the conductive stateand the third transistor 212 is in the non-conductive state. Thecapacitance of the fourth stage is the capacitance of thecharge-to-voltage converter when the first transistor 210, the secondtransistor 211, and the third transistor 212 are in the conductivestate. Note that the sensitivity control signal φ212(n) can be driven tothe active level. An operation in this case is the same as in the secondembodiment.

The thresholds and driving operations of the first transistor 210 andthe second transistor 211 will now be described with reference to FIG.13 . FIG. 13 shows the driving operations of the first transistor 210,the second transistor 211, the third transistor 212, and the resettransistor 204 in a readout operation of a pixel signal. In operation A,sensitivity control signals φ210, φ211, and φ212 are set to the activelevel (the first transistor 210, the second transistor 211, and thethird transistor 212 are ON). Furthermore, in operation A, a resetsignal φ204 changes like a pulse. This resets the capacitances of the FD203, the first transistor 210, the second transistor 211, and the thirdtransistor 212. In operation B, the signals φ210, φ212, and φ204 are setto the active level (the first transistor 210, the third transistor 212,and the reset transistor 204 are ON). Furthermore, in operation B, thesignal φ211 changes like a pulse. This resets the capacitances of the FD203 and the first transistor 210. In operation C, the signals φ211 andφ204 are set to the active level (the second transistor 211 and thereset transistor 204 are ON). Furthermore, in operation C, the signalφ210 changes like a pulse. This resets the FD 203.

The third capacitance that is added to the third node n3 when the thirdtransistor 212 is set in the conductive state is preferably larger thanthe second capacitance that is added to the second node n2 when thesecond transistor 211 is set in the conductive state. This isadvantageous in providing satisfactory image quality with a low N/Sratio. The third capacitance that is added to the third node n3 when thethird transistor 212 is set in the conductive state is preferably largerthan the first capacitance that is added to the first node n1 or the FD203 when the first transistor 210 is set in the conductive state. Thisis advantageous in providing satisfactory image quality with a low N/Sratio.

In one example, the gate length of the third transistor 212 may belonger than that of the second transistor 211. In this case, the gatewidth of the third transistor 212 may or may not be equal to that of thesecond transistor 211. In one example, the gate length of the thirdtransistor 212 may be longer than that of the first transistor 210. Inthis case, the gate width of the third transistor 212 may or may not beequal to that of the first transistor 210.

The threshold of the third transistor 212 can sufficiently be decreasedand the threshold of the second transistor 211 can sufficiently beincreased. For example, the threshold of the third transistor 212 can bemade smaller than that of the second transistor 211. As described in thesecond embodiment, this arrangement is advantageous in improving thelinearity characteristics and improving the dynamic range.

To increase the capacitances of the first transistor 210 and the thirdtransistor 212, the areas of the second transistor 211 and the resettransistor 204 may be made smaller than those of the first transistor210 and the third transistor 212. The areas of the second transistor 211and the reset transistor 204 can be made, for example, equal to eachother.

As exemplified in FIG. 12 , the first transistor 210 and the secondtransistor 211 can be arranged in a rectangular portion of an activeregion including the rectangular portion. Alternatively, as exemplifiedin FIG. 12 , the first transistor 210, the second transistor 211, andthe third transistor 212 can be arranged in a rectangular portion of anactive region including the rectangular portion. Alternatively, asexemplified in FIG. 12 , the first transistor 210, the second transistor211, the third transistor 212, and the reset transistor 204 can bearranged in a rectangular portion of an active region including therectangular portion.

As exemplified in FIG. 12 , the PD 201 as a photoelectric converter canhave a polygonal shape, and the channel length direction of the firsttransistor 210, the second transistor 211, and the third transistor 212can be parallel to one side of the polygon of the PD 201. Alternatively,as exemplified in FIG. 12 , the channel length direction of the firsttransistor 210, the second transistor 211, the third transistor 212, andthe reset transistor 204 can be parallel to one side of the polygon ofthe PD 201. Note that in the example of FIG. 12 , the channel lengthdirection of the first transistor 210, the second transistor 211, thethird transistor 212, and the reset transistor 204 is the horizontaldirection on a paper surface.

An example of a photoelectric conversion system using a photoelectricconversion device of each of the above-described embodiments will bedescribed below.

FIG. 14 is a block diagram showing the arrangement of a photoelectricconversion system 1200 according to this embodiment. The photoelectricconversion system 1200 according to this embodiment includes aphotoelectric conversion device 1215. Any one of the photoelectricconversion devices described in the above embodiments can be applied asthe photoelectric conversion device 1215. The photoelectric conversionsystem 1200 can be used as, for example, an image capturing system.Practical examples of the image capturing system are a digital stillcamera, a digital camcorder, and a monitoring camera. FIG. 14 shows anexample of a digital still camera as the photoelectric conversion system1200.

The photoelectric conversion system 1200 shown in FIG. 14 includes thephotoelectric conversion device 1215, a lens 1213 for forming an opticalimage of an object on the photoelectric conversion device 1215, anaperture 1214 for changing the amount of light passing through the lens1213, and a barrier 1212 for protecting the lens 1213. The lens 1213 andaperture 1214 form an optical system for concentrating light to thephotoelectric conversion device 1215.

The photoelectric conversion system 1200 includes a signal processor1216 for processing an output signal output from the photoelectricconversion device 1215. The signal processor 1216 performs an operationof signal processing of performing various kinds of correction andcompression for an input signal, as needed, thereby outputting theresultant signal. The photoelectric conversion system 1200 furtherincludes a buffer memory unit 1206 for temporarily storing image dataand an external interface unit (external I/F unit) 1209 forcommunicating with an external computer or the like.

Furthermore, the photoelectric conversion system 1200 includes arecording medium 1211 such as a semiconductor memory for recording orreading out image capturing data, and a recording medium controlinterface unit (recording medium control I/F unit) 1210 for performing arecording or readout operation in or from the recording medium 1211. Therecording medium 1211 may be incorporated in the photoelectricconversion system 1200 or may be detachable.

In addition, communication with the recording medium 1211 from therecording medium control I/F unit 1210 or communication from theexternal I/F unit 1209 may be performed wirelessly.

Furthermore, the photoelectric conversion system 1200 includes a generalcontrol/arithmetic unit 1208 that controls various kinds of operationsand the entire digital still camera, and a timing generation unit 1217that outputs various kinds of timing signals to the photoelectricconversion device 1215 and the signal processor 1216. In this example,the timing signal and the like may be input from the outside, and thephotoelectric conversion system 1200 need only include at least thephotoelectric conversion device 1215 and the signal processor 1216 thatprocesses an output signal output from the photoelectric conversiondevice 1215. As described in the fourth embodiment, the timinggeneration unit 1217 may be incorporated in the photoelectric conversiondevice. The general control/arithmetic unit 1208 and the timinggeneration unit 1217 may be configured to perform some or all of thecontrol functions of the photoelectric conversion device 1215.

The photoelectric conversion device 1215 outputs an image signal to thesignal processor 1216. The signal processor 1216 performs predeterminedsignal processing for the image signal output from the photoelectricconversion device 1215 and outputs image data. The signal processor 1216also generates an image using the image signal. Furthermore, the signalprocessor 1216 may perform distance measurement calculation for thesignal output from the photoelectric conversion device 1215. Note thatthe signal processor 1216 and the timing generation unit 1217 may beincorporated in the photoelectric conversion device. That is, each ofthe signal processor 1216 and the timing generation unit 1217 may beprovided on a substrate on which pixels are arranged or may be providedon another substrate. An image capturing system capable of acquiring ahigher-quality image can be implemented by forming an image capturingsystem using the photoelectric conversion device of each of theabove-described embodiments.

The photoelectric conversion system and a moving body according to thisembodiment will be described with reference to FIGS. 15A, 15B and 16 .FIGS. 15A and 15B are schematic views showing an example of thearrangement of the photoelectric conversion system and the moving bodyaccording to this embodiment. FIG. 16 is a flowchart illustrating theoperation of the photoelectric conversion system according to thisembodiment. This embodiment will describe an example of an in-vehiclecamera as the photoelectric conversion system.

FIGS. 15A and 15B show an example of a vehicle system and aphotoelectric conversion system that is incorporated in the vehiclesystem and performs image capturing. A photoelectric conversion system1301 includes a photoelectric conversion device 1302, an imagepreprocessor 1315, an integrated circuit 1303, and an optical system1314. The optical system 1314 forms an optical image of an object on thephotoelectric conversion device 1302. The photoelectric conversiondevice 1302 converts, into an electrical signal, the optical image ofthe object formed by the optical system 1314. The photoelectricconversion device 1302 is one of the photoelectric conversion devicesaccording to the above-described embodiments. The image preprocessor1315 performs predetermined signal processing for the signal output fromthe photoelectric conversion device 1302. The function of the imagepreprocessor 1315 may be incorporated in the photoelectric conversiondevice 1302. In the photoelectric conversion system 1301, at least twosets of the optical systems 1314, the photoelectric conversion devices1302, and the image preprocessor 1315 are arranged, and an output fromthe image preprocessor 1315 of each set is input to the integratedcircuit 1303.

The integrated circuit 1303 is an image capturing system applicationspecific integrated circuit, and includes an image processor 1304 with amemory 1305, an optical distance measurement unit 1306, a distancemeasurement calculation unit 1307, an object recognition unit 1308, andan abnormality detection unit 1309. The image processor 1304 performsimage processing such as development processing and defect correctionfor the output signal from each image preprocessor 1315. The memory 1305temporarily stores a captured image, and stores the position of a defectin the captured image. The optical distance measurement unit 1306performs focusing or distance measurement of an object. The distancemeasurement calculation unit 1307 calculates distance measurementinformation from a plurality of image data acquired by the plurality ofphotoelectric conversion devices 1302. The object recognition unit 1308recognizes objects such as a vehicle, a road, a road sign, and a person.Upon detecting an abnormality of the photoelectric conversion device1302, the abnormality detection unit 1309 notifies a main control unit1313 of the abnormality.

The integrated circuit 1303 may be implemented by dedicated hardware, asoftware module, or a combination thereof. Alternatively, the integratedcircuit may be implemented by an FPGA (Field Programmable Gate Array),an ASIC (Application Specific Integrated Circuit), or a combinationthereof.

The main control unit 1313 comprehensively controls the operations ofthe photoelectric conversion system 1301, vehicle sensors 1310, acontrol unit 1320, and the like. A method in which the photoelectricconversion system 1301, the vehicle sensors 1310, and the control unit1320 each individually include a communication interface andtransmit/receive control signals via a communication network (forexample, CAN standards) may be adopted without providing the maincontrol unit 1313.

The integrated circuit 1303 has a function of transmitting a controlsignal or a setting value to each photoelectric conversion device 1302by receiving the control signal from the main control unit 1313 or byits own control unit.

The photoelectric conversion system 1301 is connected to the vehiclesensors 1310 and can detect the traveling state of the self-vehicle suchas the vehicle speed, the yaw rate, and the steering angle, the externalenvironment of the self-vehicle, and the states of other vehicles andobstacles. The vehicle sensors 1310 also serve as a distance informationacquisition unit that acquires distance information to a target object.Furthermore, the photoelectric conversion system 1301 is connected to adriving support control unit 1311 that performs various driving supportoperations such as automatic steering, adaptive cruise control, andanti-collision functions. More specifically, with respect to a collisiondetermination function, based on the detection results from thephotoelectric conversion system 1301 and the vehicle sensors 1310, acollision with another vehicle or an obstacle is estimated or thepresence/absence of a collision is determined. This performs control toavoid a collision when the collision is estimated or activates a safetyapparatus at the time of a collision.

Furthermore, the photoelectric conversion system 1301 is also connectedto an alarming device 1312 that generates an alarm to the driver basedon the determination result of a collision determination unit. Forexample, if the determination result of the collision determination unitindicates that the possibility of a collision is high, the main controlunit 1313 performs vehicle control to avoid a collision or reduce damageby braking, releasing the accelerator pedal, or suppressing the engineoutput. The alarming device 1312 sounds an alarm such as a sound,displays alarming information on the screen of a display unit such as acar navigation system or a meter panel, or applies a vibration to theseat belt or a steering wheel, thereby giving an alarm to the user.

The present invention is not limited to the above embodiments andvarious changes and modifications can be made within the spirit andscope of the present invention. Therefore, to apprise the public of thescope of the present invention, the following claims are made.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all such modifications and equivalent structures andfunctions.

This application claims the benefit of Japanese Patent Application No.2021-016039, filed Feb. 3, 2021, which is hereby incorporated byreference herein in its entirety.

What is claimed is:
 1. A photoelectric conversion device comprising: aphotoelectric converter provided at a substrate; a first node configuredto be supplied with charges from the photoelectric converter; anamplification transistor configured to output a signal corresponding toa voltage of the first node to an output line via a selectiontransistor; a first transistor configured to open/close a path betweenthe first node and a second node not included in a path from thephotoelectric converter to the first node; a second transistorconfigured to open/close a path between the second node and a thirdnode; and a third transistor arranged in a path between the third nodeand a fourth node, wherein, in a planar view from a surface of thesubstrate, a first direction in which the first transistor, the secondtransistor, and the third transistor are arranged intersects a seconddirection in which the amplification transistor and the selectiontransistor are arranged.
 2. The device according to claim 1, wherein thefirst direction is a channel length direction of each of the firsttransistor, the second transistor, and the third transistor.
 3. Thedevice according to claim 1, wherein a third capacitance which is addedto the third node when the third transistor is set in a conductive stateis larger than a second capacitance which is added to the second nodewhen the second transistor is set in a conductive state.
 4. The deviceaccording to claim 1, wherein a gate length of the third transistor islonger than a gate length of the second transistor.
 5. The deviceaccording to claim 1, wherein a gate width of the third transistor isequal to a gate width of the second transistor.
 6. The device accordingto claim 1, wherein the first transistor, the second transistor, and thethird transistor are arranged in a first active region, and wherein theamplification transistor is arranged in a second active region.
 7. Thedevice according to claim 6, wherein the selection transistor isarranged in the second active region.
 8. The device according to claim6, further comprising a reset transistor configured to open/close a pathbetween the fourth node and a predetermined voltage line, wherein thereset transistor is arranged in the first active region.
 9. Aphotoelectric conversion system comprising: a photoelectric conversiondevice according to claim 1; and a signal processor configured toprocess a signal output from the photoelectric conversion device.
 10. Amoving body comprising: a photoelectric conversion device according toclaim 1; a distance information acquisition unit configured to acquiredistance information to a target object from distance measurementinformation based on a signal from the photoelectric conversion device;and a control unit configured to control the moving body based on thedistance information.
 11. A photoelectric conversion device comprising:a photoelectric converter provided at a substrate; a first nodeconfigured to be supplied with charges from the photoelectric converter;an amplification transistor configured to output a signal correspondingto a voltage of the first node to an output line via a selectiontransistor; a first transistor configured to open/close a path betweenthe first node and a second node not included in a path from thephotoelectric converter to the first node; a second transistorconfigured to open/close a path between the second node and a thirdnode; and a third transistor arranged in a path between the third nodeand a fourth node, wherein, in a planar view from a surface of thesubstrate, a first direction in which a gate of the first transistor, agate of the second transistor, and a gate of the third transistor arearranged intersects a second direction in which a gate of theamplification transistor and a gate of the selection transistor arearranged.
 12. The device according to claim 11, wherein a source of theamplification transistor and a drain of the selection transistor, or adrain of the amplification transistor and a source of the selectiontransistor are arranged in the second direction.
 13. A photoelectricconversion system comprising: a photoelectric conversion deviceaccording to claim 11; and a signal processor configured to process asignal output from the photoelectric conversion device.
 14. The deviceaccording to claim 11, wherein the first direction is a channel lengthdirection of each of the first transistor, the second transistor, andthe third transistor.
 15. The device according to claim 11, wherein athird capacitance which is added to the third node when the thirdtransistor is set in a conductive state is larger than a secondcapacitance which is added to the second node when the second transistoris set in a conductive state.
 16. The device according to claim 11,wherein a gate length of the third transistor is longer than a gatelength of the second transistor.
 17. The device according to claim 11,wherein a gate width of the third transistor is equal to a gate width ofthe second transistor.
 18. The device according to claim 11, wherein thefirst transistor, the second transistor, and the third transistor arearranged in a first active region, and wherein the amplificationtransistor is arranged in a second active region.
 19. The deviceaccording to claim 11, wherein the selection transistor is arranged inthe second active region.
 20. The device according to claim 11, furthercomprising a reset transistor configured to open/close a path betweenthe fourth node and a predetermined voltage line, wherein the resettransistor is arranged in the first active region.
 21. A photoelectricconversion system comprising: a photoelectric conversion deviceaccording to claim 15; and a signal processor configured to process asignal output from the photoelectric conversion device.
 22. A movingbody comprising: a photoelectric conversion device according to claim11; a distance information acquisition unit configured to acquiredistance information to a target object from distance measurementinformation based on a signal from the photoelectric conversion device;and a control unit configured to control the moving body based on thedistance information.